Tectonic property of late Paleozoic garnet-bearing high-P/T schist at the boundary between the Nedamo and North Kitakami belts, NE Japan

Abstract

: An exotic block of garnet-bearing schist has been found at the boundary between the Early Triassic Takinosawa Unit of the Nedamo Belt and the Early Jurassic Nakatsugawa Complex of the North Kitakami Belt, NE Japan. This is only the second discovery of exotic schists in the Nedamo Belt; the previously identi-fied schists occur at the boundary between the Takino sawa and early Carboniferous Tsunatori units of the Nedamo Belt. The garnet-bearing schist is character-ized by a mineral assemblage of garnet + phengite + epidote + albite + quartz + titanite. Phengite with Si of 6 . 51 – 6 . 66 atoms per formula unit (O = 22 ) and the mineral assemblage suggest that the schist underwent high- P/T metamorphism prior to emplacement into its current position. The schist yields a phengite K–Ar age of ca. 290 Ma (late Paleozoic), suggesting a correlation with high- P/T schist of the Yamagami Metamorphic Rocks from the Motai–Matsugadaira Belt. This finding supports the extension of late Paleozoic high- P/T metamorphic rocks (i.e., the Renge Belt of SW Japan) to NE Japan.